I know this is getting technical but use a meter Brett. Chargers usually are putting out about 1.5 v or.higher over what they are charging. I've had 12v chargers putting out 14.5v So check your chargers output when you apply a load (connect it to the battery for a moment) however if your charger is not a "smart charger" which switches voltage to standby and "floats" the batteries charge you should do some basic math a remeber to disconnect the charger to prevent overcharging.

The charge rate (indicated by ca) is multiplied by capacity. So .3 x 12ah is 3.6 Amp max charge rate. At this rate your battery will be fully charged in about 3.5 hours. At a rate 300 mah your battery would go from dead to full charge in 40 hours. That would take forever so for this battery , a larger charger would be in order lol. You may want to just go to walmart and get a 2ah smart charger for motorcycles and you can charge your battery from dead to max in a little over 6 hours. And a smart charger automatically switches to a lower floating voltage once your battery is full ;D. My charger was a atv/moto charger in auto section.

is even better (fast charge etc...) but needs to be controlled by hand. I mean, you must selectthe charge mode and press a start button. Not always handy. It's a little more expensive but alsocapable of higher capacity batteries. Quite good !

SLA batteries especially, need a charger that will automaticaly decrease the charge rate as the battery approaches full. When a battery is empty it'll suck-up many amps no problem, but the closer it gets to full the less it's eager to suck-up those amps, and the excess becomes heat. Heat evaporates your electrolyte, slowly at first, but can become a full on boil if you forget about it. On older style flooded batteries this isn't an issue (and in fact, a good boil is sometimes beneficial on occasion), because they are basicly open topped & very easily refillable. But on SLA batteries, there's a safety vent to release excess pressure from evaporating electrolyte (some do feature a chamber that holds onto the gas, to let it condense back into the battery later, but they only hold so much before again venting comes into play), but no way to refill it, so once it's gone it's gone. In severe cases, you can actually cause an SLA battery pop wide open (I've had it happen in my computer's UPS and my wheelchair), which creates a lovely cloud of sulfuric acid gas until you figure it out & disconnect the charger.

Take care of your batteries & they'll reward you with a long life, abuse them & you'll quickly need new ones.

What I did , Bret, was purchase two jet-ski batteries. They come in either 6 or 12 Volts. Mine are 12vdc. They are sealed and can be operated in Extreme conditions tipped over and even upside down without spilling. They are Perfect! B4 this, I tried a simple sealed auto battery and it overcharged and left a big hole in my brand new carpet. That did not make me very popular with the wife. She told me I had to take Leaf Outside from then on. I finally talked my way out of it for Leaf and myself. But, it was a close call. So, I got the jet-ski batteries and forgot about it.

Bret ndavid79 is right on about charging any sla,agm or gells. A small Schumacher charger like jstarne1 posted would work good. Only thing bad about any lead acid is you can't discharge them much . A 12v discharged to 10.5v is considered 100% discharged! (I don't know the v for a 6v) Also you do not want to leave them stored in a discharged state ! Big no no! It will cause them sulphate and eventually make the useless. JW. PS I have over 50 batteries I keep charged with Schumacher chargers.